The present invention relates to methods and compositions for treating viral infections. More specifically, the invention is directed towards the treatment of viral infections through the use of smooth muscle relaxing agents and agents that block the entry of calcium ions (Ca.sup.++) into cells. These agents appear to act by blocking replication of the target viruses in infected cells.
Advances in the treatment of viral infections have been very slow in coming. Very few efficacious antiviral agents presently exist. A few agents have been touted for their potentially specific antiviral activity are in the research and development stage. The clinical efficacy of these agents, such as interferon and interferon inducers (e.g., polyanionic pyran copolymers and double stranded RNA) have yet to be reproducibly demonstrated.
A few pharmaceutical agents have shown promise in the treatment of isolated viral infections, including the use of amantadine in the treatment of Influenza A.sub.2 strains. The use of the antimetabolities, Idoxuridine and Cytarabine, in antiviral therapy is hampered by a narrow spectrum of activity and potentially severe side effects. Methisazone is receiving some support for its use against some pox and vaccinia strains. Its use in pox infections is generally limited to prophylaxis. In general, there are presently no efficacious antiviral agents that demonstrate a broad spectrum of activity. It now appears that no single broad spectrum agent, or family of agents, may be identified as useful in antiviral treatment. Therefore, research is being directed towards identifying antiviral agents with activity against selected viral diseases.
A novel approach to the treatment of certain viral diseases, including human cytomegalovirus (HCMV), varicellazoster virus, and herpes simplex virus, is addressed by the present invention. This approach involves the restriction of viral expression and replication in infected cells by controlling and modifying the cellular responses to viral infection.
HCMV causes acute and apparently life-long persistent infections of man (T. H. Weller, N. Eng. J. Med. 285:203-214, 267-274 (1971)). HCMV infection has been determined the causative agent in a number of birth defects, including microencephalopathy, hydroencephelopathy and microthalmia. Other defects associated with pre-natal HCMV infections include severe mental retardation, disordered hepatic function, and hyperbilirubinemia. Although the disease is often asymptomatic in children and adults, HCMV infections in these groups have been shown to result in enlargement of the liver and spleen and deranged erythropoesis. The disease may remain dormant for years, then reactivated by unknown causes. Localized and generalized HCMV infections have been shown to develop after immuno-suppressive and anti-neoplastic therapy. HCMV is a member of the herpes family of viruses.
The most widely recognized feature of HCMV-induced cytopathology is the formation of distinct nuclear and cytoplasmic inclusions (CI's) (T. Albrecht, T. Cavello, N. L. Cole, and K. Graves, Lab. Invest., 42:1-7 (1980)). Another HCMV cytopathic effect involves the rounding of fibroblastic cells beginning within the first several hours after infection. By 12-24 hours post-infection, depending on the intensity of the infection, nearly all cells are small and rounded.
The novel approach to restrict virus expression and replication presented by the present invention is to control the cellular response to virus infection. Such approaches may be particularly warranted for human cytomegalovirus since this virus is an important cause of disease for which effective therapeutic agents have not yet been identified. Additionally, as previously noted, HCMV infections present notable changes in cytopathology which suggest that cytopathic-directed therapy might prove particularly efficacious in the treatment of that disease.